The overall goal of this project is to develop a novel approach for the treatment of drug abuse using unique and patented biodegradable injectable gel formulations which can control the release of naltrexone. These novel biodegradable get formulations wit maintain therapeutic concentrations of naltrexone for at least 4 weeks, following a single subcutaneous injection, thereby creating a product that will overcome the major disadvantages of current mode of oral therapy, i.e. significant first pass metabolism and poor patient compliance. Therefore, the specific aims of this study are as follows: (1) Develop and Evaluate In Vitro Drug Release Rates from Novel Injectable Gels Loaded with Naltrexone. The first step in this study is to prepare drug-loaded gel formulations with varying formulation factors and ascertain in vitro release rates of naltrexone from the gel formulations. (2) Ascertain Biodegradability, Biocompatibility of the Gels and How Long Constant Plasma Concentrations of Naltrexone can be Maintained in Vivo after a Single Subcutaneous Injection. Biodegradability and biocompatibility of the drug-loaded gels and the duration of maintaining constant plasma concentration of naltrexone released from two optimized drug-loaded gel formations will be examined in rats following a single subcutaneous injection of the gels. PROPOSED COMMERCIAL APPLICATION: A parenterally administered formulation of a narcotic antagonist that is biodegradable and can release the drug at a controlled rate over a 2-4 week period following a single injection would be important in the treatment of opiate dependence. The potential commercial implications of such drug delivery system will be significant not only in the field of opiate abuse treatment, but also in the treatment of alcoholism, a much larger and economically devastating problem in our society today. A U.S. patent application for this system is pending and is expected to be granted shortly. Therefore, we believe that an issued patent and data generated from both Phase I and phase II studies will help us commercialize the technology and make a viable product.